Boost it baby!

[max_torque]

Originally posted by PeterS
I thought the overboost spike was just a classic sinusoidal PID overshoot as the system tries to match the requested boost (assuming step function


Mike (Jabba) seemed to be able to tune the PID to minimalise overshoot for me, at the expense of a bit of extra lag...at least thats my perception

Peter

yes i think that what i was trying to say!

As i mentioned the control is a set of comprimises, so to get a stable system in your case meant having to damp the systems responses, leading to perhaps some more lag on tip-ins.

I didn't mean to say that all tuners don't know there arse from the elbow, there are some good ones (But they are in the minority, especialy when cars with really complicated control systems are the subject)
the main problem really is trying to make it profitable, even if the tuners have the skills, if they spent enough time on the remapping to do close to an QEM job, then they would have to charge £2000 a "chip" to make it pay at the numbers they sell, afterall VW struggle to do pay for the original calibration any they are selling 100,000's of cars!

The really good guys will spend just that bit extra time getting things right for a customer, becuase they know that reputation counts more than a quick buck in the aftermarket tuning game, especially in this internet age when an entire "comunity" of owners can read that so-and-so is rubish etc on just one afternoon.

 

[PeterS]

yes i think that what i was trying to say!

Your version was much more interesting though!

Is the "ramp rate" also dependant on fueling/air flow rate (ie throttle position) as well as engine speed? I'm guessing there's some non-linear relationships involved here, hence the need for boost multiplier tables(?)

Peter

 

[Shock_Xe]

wow its like reading a book at the end of the thread! :hammer:

As far as Revo goes i hit a brick wall at an 'indicated' 140mph! have gone to 143. Pulls like a train upto 125/130 but after that very creepy both on low and high 9! Hopefully the new k03s and remap should give me an extra shove top end!

 

[ibizacupra]

When Oettingered many moons ago... The car went to an indicated 155mph a few times...

Speedo is way optomistic however... 10% of reading error by my reckoning.

Not much boost from the Oettinger and done on a cold late night on a private road.

 

[ibizacupra]

Originally posted by max_torque
depends upon the car / ecu.

In the strategy for the 1.8t there is a "boost" multiplier table and ramp rate agaisnt engine speed to introduce an "overboost" which decays away to the static boost level after a calibrated number of engine cycles.

But typically it's because you are cruising along at a low throttle opening, the boost request is close to zero so the N75 duty cycle is also close to zero, then you slam you foot to the floor, the new chipped requested boost is suddenly massively bigger than the actual boost being delievered, therefore the boost error or proportional term is huge, so the duty cycle controller slams the N75 duty to 100%, shutting the wastegate, sending boost pressure skyrocketing upwards, straight past the set point, when suddenly the reverse set of symptoms is present and boost pressure will now undershoot the target. After a few cycles this will damp out in all but the worst cases, as the basic hardware set up is a negative feedback system.

Although the average owner does not tend to notice anything but the most serious driveability issues, and quickly adapts to drive around these, people in the buisness of engine calibration like myself can spot a chipped cars a mile off!

Its a bit of kidology I think and preference from tuners as to how they choose to deliver the power. My old Oettinger chip was very aggresive at the time on its overboost, and felt 'fast' as it shoved you in the back immediately. The urgency did'nt last however and soon tailed off to very medeocre boost levels dropping very low as the revs climbed. Back then, APR Europe (now REVO) had a must smoother power delivery but sustained the boost @ 1 bar for most of the rev range. Drove smooth, but lacked the 'fizz' I had got used to with the Oettinger. On track however... and mine was still no slower (marginally faster) than APR down Bruntingthorpe straight, from less power.??? (lower boost less heatsoak I presumed given the track activity)

Mike @ Jabba will tailor the power delivery to the customers wants. The power delivery can be smooth or very aggressive. My preference is smooth and progressive, but sustained.

regards
bill

 

[Madmile]

I just think sustained boost is better the k03 die's on its arse as it is high up the revs, anything you can do to sustain boost high up the revs the better i think in my opinion, but each to there own.

 

[BenS1]

Originally posted by max_torque
depends upon the car / ecu.

In the strategy for the 1.8t there is a "boost" multiplier table and ramp rate agaisnt engine speed to introduce an "overboost" which decays away to the static boost level after a calibrated number of engine cycles.

But typically it's because you are cruising along at a low throttle opening, the boost request is close to zero so the N75 duty cycle is also close to zero, then you slam you foot to the floor, the new chipped requested boost is suddenly massively bigger than the actual boost being delievered, therefore the boost error or proportional term is huge, so the duty cycle controller slams the N75 duty to 100%, shutting the wastegate, sending boost pressure skyrocketing upwards, straight past the set point, when suddenly the reverse set of symptoms is present and boost pressure will now undershoot the target. After a few cycles this will damp out in all but the worst cases, as the basic hardware set up is a negative feedback system.

Although the average owner does not tend to notice anything but the most serious driveability issues, and quickly adapts to drive around these, people in the buisness of engine calibration like myself can spot a chipped cars a mile off!

Whilst that whole system sounds complex, when you actually think about it its very simplistic, in fact I think its too simplistic.

As you say, the system requests a certain boost level and overshoots the mark (eg. starting boost = 2psi (Cruising), target = 12psi (Floored it) but it shoots past 12psi and hits 16psi.). By why is the system not 'intellegent' enough to know that its likely to overboost? ie. in my example it could target 12psi and so close the wastegate etc, and then knowing that it takes time to react it could start to open the wastegate at say 8psi so that it manages to stop the boost rise at exactly 12psi (Obviously it would then have to close the wastegate a little to stop the boost dropping back below 12psi).

As a computer programmer I think this is very simple to implement. Of course thats providing you have this level of control over how the ECU works.

So heres hwat I think is happening:

And heres what I would say should happen:

Does that look right, or am I on something?

Cheers
Ben

 

[max_torque]

Basically Ben, the system is capable of minimising errors, but it needs to be correctly calibrated and matched to the system that it is controlling, the issue in chipped cars is that the enviroment of the control system has significantly changed, but no one has re-calibrated the control systems response, hence over or under boost etc.

Modern ECU's now contain significant "adaptive" strategy, that will look at the way a control system is functioning, and using a set of calibrated criteria will effectively rate it's system errors, and adapt the control systems strategy to minimise these error. This is vital to allow close and repeatable control on hardware / environments that is not nominal or has aged. Ot's the reason that we now need to run significant "preconditioning" cycles, or download certain nominal learned parameters before we attempt to calibrate various emissions and driveability functions.

 

[CustardCupra]

Originally posted by monty77
Don't know about the other Revo boys but I get sod all acceleration past 120-125mph, feels like it hits a brick wall

CTRs always creep past me at that point too, most upsetting

A

Would take the car back to REVO and ask what the Feck is going on ,
Personally i can see 155MPH indicated on AMD chip and MILLTEK SPORT CAT AND DOWNPIPE ,
And thats while i go past a REVO equipped IBIZA ( Hitting a brick wall @ 140 mph ) .
"PROVEN"

Have had AMD chip for over 2 years now and i can't fault it .
Initial boost spike is 16psi holding 14 till 5500 rpm then 8 ish @ 6800 rpm .

Never had a CTR get close let alone come past ,

theres obviosly alot to be said for a personall map rather than generic.

 

[BenS1]

Yeah I've gone past 140 before and it was still pulling, and thats with my Oettinger chipped Ibiza.

Cheers
Ben

 

[chriskaven]

My generic REVO map is good!

I have the REVO optimax code with no SPS and only a dynatwist air filter.

Mine peaks at 1.35bar (19.6PSI) and is holding 0.6bar (8.7PSI) at 6800rpm

My ibiza will exceed 140mph where the law allows.

 

[ibizacupra]

Maybe this brick wall encountered is during warm summer months?

 

[monty77]

Originally posted by ibizacupra
Maybe this brick wall encountered is during warm summer months?

'fraid not. Gave it a go on Monday, past 120 acceleration was very slow. Beginning to think I have a problem.

A

 

[BenS1]

Originally posted by chriskaven
My generic REVO map is good!

I have the REVO optimax code with no SPS and only a dynatwist air filter.

Mine peaks at 1.35bar (19.6PSI) and is holding 0.6bar (8.7PSI) at 6800rpm

My ibiza will exceed 140mph where the law allows.

I just don't understand why your boost at the limit is so low. Mine doesn't drop below 12psi, and my chip (Oettinger) is considered to be pretty 'last generation' now.

Cheers
Ben

 

[ibizacupra]

Originally posted by BenS1
I just don't understand why your boost at the limit is so low. Mine doesn't drop below 12psi, and my chip (Oettinger) is considered to be pretty 'last generation' now.

Cheers
Ben

My Oettinger dropped to those levels at max revs also.
Still did 155 inidicated if you gave it long enough tho.

 

[ibizacupra]

Originally posted by monty77
'fraid not. Gave it a go on Monday, past 120 acceleration was very slow. Beginning to think I have a problem.

A

Be worth datalogging mass airflow, ignition timing, requested vs actual boost and induction temps (on a private road)

 

[chriskaven]

Maybe oettinger run closer to knock limit than REVO at the top end?

Of the oettinger power/torque curves that I have compared with the standard REVO curves, it seems that torque values (peak and area and under the curve) seem greater for REVO than oettinger. Power curves seem to have similar peaks although the oettinger seems to hold the power for longer.

We should also consider spark timing - maybe REVO rely more on boost to get the power/torque whereas oetinger using more spark advance?

 

[monty77]

Originally posted by ibizacupra
Be worth datalogging mass airflow, ignition timing, requested vs actual boost and induction temps (on a private road)

Dont suppose you've got a list of blocks I should be measuring to do that? And step by step how to do this? Pretend I'm an idiot

Cheers,
A

 

[Madmile]

My poor old superchipped ibiza does 151mph not a problem, no brick wall at 120-130mph. There again i have raced a revo'd ibiza and was to quick for it in straight line run, more towards 120-130mph+ though this is where the revo'd seemed slower. My boost spikes 17-18psi and drops to 8-10psi at redline. The brick wall for me is 151mph. E-05 should cure the 151mph brick wall. I know i can ourun a Audi tt225 in a straight line blast.

 

[ibizacupra]

Originally posted by chriskaven
Maybe oettinger run closer to knock limit than REVO at the top end?

Of the oettinger power/torque curves that I have compared with the standard REVO curves, it seems that torque values (peak and area and under the curve) seem greater for REVO than oettinger. Power curves seem to have similar peaks although the oettinger seems to hold the power for longer.

We should also consider spark timing - maybe REVO rely more on boost to get the power/torque whereas oetinger using more spark advance?

Oettinger does run aggressive ignition timing.. Not sure how it compares to REVO, but it was more than APR way back in 2001.

My Oettinger power was only ~190bhp so not top notch.
High sustained boost WOT will get the induction hot, and REVO'd sustained boost and initial boost is much higher than Oettinger.

Some cars do run better than others... Ibiza factor X